1. Field of the Invention
The present invention relates to resinous coating compositions which contain N-methylol amide groups.
2. DESCRIPTION OF THE PRIOR ART
Resinous materials comprising various forms of N-methylol groups such as etherified N-methylol groups are known as being useful in enhancing cure properties of coating compositions. Although coating compositions containing free N-methylol groups are highly reactive and well suited to enhance curing properties, they are not favored because of their high reactivity and particular susceptibility to condensation reaction with themselves and with other sources of active hydrogens. Consequently, resinous materials and for that matter coating compositions containing free N-methylol groups, in amounts sufficient to effect good cure have been difficult to prepare and handle. When used in amounts sufficient to impart good cure properties, the resinous materials comprising free N-methylol groups can gel prematurely and become ineffective as coating compositions.
In consideration of the foregoing, the art has stayed clear of using free N-methylol groups in amounts which will otherwise cure very well. Instead, the N-methylol groups are either used in forms that are less reactive, e.g., in etherified forms, or in amounts which are not sufficient to effectively enhance cure properties.
The present invention, in contrast, provides stable aqueous resinous compositions containing free N-methylol groups in the form of N-methylol amide in amounts sufficient to impart excellent cure properties at comparatively low temperatures.